Network router that efficiently switches between a primary data path and a backup data path

ABSTRACT

A network router initially communicates over a primary data path. Upon detection of an error condition associated with the primary data path, the network router initiates a layer 2 switch such that the communication occurring over the primary data path is switched to a backup data path. The layer 2 switch is preferably transparent to a layer 3 portion of the network router.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 60/472,685, entitled “System and Method for Backing Up a Data Path for a Network Router,” and filed on May 22, 2003, which is incorporated herein by reference.

RELATED ART

In current communication networks, routers employ communication backup techniques that enable such routers to communicate over an alternative data path in the event that a primary data path is interrupted or fails. As an example, it is common for a router to communicate over a primary data path using a high speed communication link, such as a T1 link, for example. If a network failure occurs such that the communication over the primary data path fails or is significantly degraded, then the router is configured to establish a secondary data path using an alternative communication link and to switch communication from the primary data path to the secondary data path. Thus, communication with the router may be resumed in the event that a communication error or failure prevents or degrades communication over the primary data path.

Note that the alternative communication link typically communicates at a slower speed and/or higher cost than the communication link of the primary data path. Therefore, it is often more desirable to communicate over the primary data path in lieu of the secondary data path in the absence of a significant communication problem along the primary data path.

Unfortunately, it takes a finite amount of time for a router to detect the occurrence of a communication error or failure along the primary data path and to then switch to communicating over the secondary data path. During this finite time period, the router typically attempts to transmit over the primary data path resulting in the loss of data, and such a loss of data can be significant depending on the length of the finite time period. Thus, techniques for reducing the amount of time for detecting communication problems along the primary data path and/or switching to the secondary data path are generally desirable.

SUMMARY

Embodiments of the present invention pertain to network routers that efficiently switch between a primary data path and a backup data path.

A network router in accordance with one exemplary embodiment of the present invention comprises a layer 1 portion, a layer 2 portion, a layer 3 portion, and switching logic. The layer 1 portion has a first communication interface and a second communication interface. The first communication interface is configured to communicate with a first network over a first data path, and the second communication interface is configured to communicate with a second network over a second data path. The layer 3 portion has a routing table and is configured to provide a plurality of data packets destined for a particular destination. The layer 2 portion is configured to interface at least one of the data packets with the first communication interface. The switching logic is configured to automatically initiate a layer 2 switch such that the layer 2 portion begins to interface the data packets with the second communication interface in lieu of the first communication interface, wherein the layer 2 switch is transparent to the layer 3 portion.

A network router in accordance with another exemplary embodiment of the present invention comprises a first protocol stack, a second protocol stack, a third protocol stack, a plurality of network interfaces, and switching logic. The first protocol stack is configured to provide a plurality of data packets to be transmitted by the router to a particular destination. The plurality of network interfaces is configured to receive data packets from the first protocol stack, wherein the first protocol stack is configured to provide each of the plurality of data packets to one of the network interfaces. The switching logic is configured to receive each of the plurality of data packets from the one network interface. The switching logic is further configured to provide at least one of the plurality of data packets to the second protocol stack and to provide, in response to a detection of an error condition, at least one other of the plurality of said data packets to the third protocol stack.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the invention. Furthermore, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a block diagram illustrating a conventional internet protocol (IP) network.

FIG. 2 is a block diagram illustrating one embodiment of a router depicted in FIG. 1.

FIG. 3 is a block diagram illustrating another embodiment of a router depicted in FIG. 1.

FIG. 4 is a block diagram illustrating an exemplary embodiment of a communication network in accordance with the present invention.

FIG. 5 is a block diagram illustrating an exemplary embodiment of a router depicted in FIG. 4.

FIG. 6 is a flow chart illustrating an exemplary architecture and functionality of monitoring logic depicted in FIG. 5.

FIG. 7 is a block diagram illustrating an exemplary configuration of the router depicted in FIG. 5.

DETAILED DESCRIPTION

FIG. 1 depicts a typical internet protocol (IP) network 15 of the prior art. For simplicity, the network 15 is shown in FIG. 1 as having two routers 17 and 19 capable of communicating to one another via a primary network 22, such as a frame relay network, for example, and/or a secondary network 25, such as the public switched telephone network (PSTN), for example. However, it should be noted that a conventional IP network 15 typically employs many additional routers (e.g., several thousand) in which each router is capable of communicating to other routers or destinations via an arrangement similar to the one depicted by FIG. 1.

Routers 17 and 19 and their corresponding digital service units (DSUs) 37 and 39 are initially configured to communicate with one another via primary network 22. Thus, the digital service unit (DSU) 37 corresponding to router 17 is coupled to the primary network 22 via a connection 31, such as a T1 connection, for example, and the DSU 39 corresponding to router 19 is coupled to the primary network 22 via a connection 33, such as a T1 connection, for example.

When the router 17 receives data to be communicated to router 19, the router 17 interfaces the data with the DSU 37, and the DSU 37 transmits the data via at least one data packet over connection 31 to primary network 22, which routes the data packet to connection 33 based on header information included in the data packet. Similarly, when the router 19 receives data to be communicated to router 17, the router 19 interfaces the data with the DSU 39, and the DSU 39 transmits the data via at least one data packet over connection 33 to primary network 22, which routes the data packet to connection 31 based on header information included in the data packet. The data path traveled by data packets communicated between routers 17 and 19 via primary network 22 shall be referred to hereafter as the “primary data path” of the network 15.

As shown by FIG. 1, the DSU 37 is also coupled to the secondary network 25 via a connection 41, such as a copper wire pair, for example, and the DSU 39 is coupled to the secondary network 25 via a connection 43, such as a twisted wire pair, for example. If a significant communication problem occurs along the primary data path, then the routers 17 and 19 and their corresponding DSUs 37 and 39 may transition to communicating via secondary network 25. In this regard, once a significant communication problem over the primary data path is detected, the router 17 and/or its corresponding DSU 37 may establish a secondary data path with DSU 39 using connections 41 and 43, as well as secondary network 25, and then utilize this secondary data path to communicate with router 19 in lieu of the primary data path passing through primary network 22. The secondary data path is typically a dedicated path in that the network 25 and the connections 41 and 43 effectively form an end-to-end connection from the DSU 37 to the DSU 39, and each set of data communicated between the routers 17 and 19 is communicated over this end-to-end connection.

Thus, when the router 17 receives data to be communicated to router 19 after the routers 17 and 19 have switched to using the secondary data path, the router 17 interfaces the data with the DSU 37, which transmits the data over connection 41 to secondary network 25 and connection 43. Similarly, when the router 19 receives data to be communicated to router 17, the router 19 interfaces the data with the DSU 39, which transmits the data over connection 43 to secondary network 25 and connection 31. The secondary data path passing through secondary network 25 is essentially used to backup the primary data path passing through the primary network 22.

There are various methodologies employed for backing up the primary data path. FIG. 2 depicts a more detailed view of a configuration of the router 17 and DSU 37 when these components are designed to perform a first type of backup, referred to hereafter as “layer 1 backup.” As shown by FIG. 2, the router 17 and its corresponding DSU 37 implement three layers (i.e., layer 1, layer 2, and layer 3) of the well-known International Organization for Standardization Open Systems Interconnection (ISO/OSI) model. In this regard, the ISO/OSI model comprises seven layers. Layer 1 is a physical layer of hardware connections. Layer 2 is a software layer responsible for coding, addressing, and transmitting information, and layer 3 is a software layer responsible for transport routes and message handling. The other layers of the ISO/OSI model are not germane to this disclosure and will not be described in detail herein.

As shown by FIG. 2, the layer 3 portion of the router 17 comprises an IP stack 52, router control logic 54, and a network interface 56. The router control logic 54 generally monitors and controls the operation of the router 17. The IP stack 52 comprises a routing table 59 that specifies a data path for each data packet received by the router 17. In this regard, when a data packet is received by the router 17, the IP stack 52 consults the routing table 59 to determine the data path that the packet is to take to reach its destination. As an example, the routing table 59 may specify that the data packet is to be routed to router 17 via the primary data path. Based on the indicated data path, the IP stack 52 inserts layer 3 route information into the header of the data packet. This information is later used to communicate the data packet across the specified data path.

Based on the specified data path, the IP stack 52 provides the data packet to the network interface 56. As shown by FIG. 2, the network interface 56 is in communication with a frame relay protocol stack 59 comprising a virtual circuit 63 and a frame relay protocol port 66. The virtual circuit 63 adds layer 2 routing information to the header of the data packet. In the embodiment shown by FIGS. 1 and 2, the primary network 22 is a frame relay network. Thus, the virtual circuit 63 appropriately processes the data packet via frame relay protocol such that the data packet is ready for transmission across the primary network 22. In other embodiments where the primary network 22 is not a frame relay network, another type of protocol stack (not shown) compatible with the primary network 22 is used in lieu of frame relay protocol stack 59. In this regard, the layer 2 protocol stack is compatible with the type of protocol employed by the primary network 22. Note that the network interface 56 is, however, typically independent of the protocol of the primary network 22, as well as the secondary network 25. Indeed, the type of primary and secondary networks 22 and 25 employed within the IP network 15 is typically transparent to layer 3 and to the network interface 56, in particular.

After processing the data packet, as described above, the router 17 provides the data packet to the DSU 37, which transmits the data packet across connection 31 to the primary network 22 (FIG. 1). In the embodiment shown by FIG. 2, a T1 interface 74 is coupled to the connection 31 and is initially used to transmit data packets received from the router 17. Thus, a switch 77 is initially set such that data packets received from the router 17 are transmitted to the T₁ interface 74.

While the router 17 is communicating according to the techniques described above, a layer 1 error condition may occur. Such an error condition typically occurs between DSU 37 and primary network 22 or between DSU 39 and primary network 22. As an example, the connection 31 may become severed and unable to communicate data. DSU control logic 82 within the DSU 37 is configured to detect the layer 1 error condition. As an example, if the connection 31 is severed, the DSU control logic 82 may detect that the connection 31 is no longer properly terminated thereby detecting a layer 1 error condition.

In response to a detection of a layer 1 error condition, the DSU control logic 82 changes the state of the switch 77 such that data packets received from the router 17 are now transmitted to a modem 88 instead of T1 interface 74. The modem 88 preferably establishes a communication session with the DSU 39 via secondary network 25. The modem 88 then communicates each received data packet over connection 41, secondary network 25, and connection 43 to the DSU 39. Thus, the secondary data path over which the modem 88 communicates, according to the aforedescribed techniques, is used to backup the communication that originally occurs via the primary data path. Note that the DSU 39 may be similarly configured to detect a layer 1 error condition and to then switch from the primary data path to the secondary data path in response to the detection of the layer 1 error condition.

Also note that the layer 1 backup performed by the DSU 37, as described above, is transparent to the router 17 and, therefore, to layers 2 and 3. In this regard, once a layer 1 error condition occurs, the router 17 continues to process each data packet as if the data packet is to be communicated over the packet's primary data path. However, the DSU 37, upon detecting the layer 1 error condition, begins to transmit the data packets over the secondary data path without the knowledge of the components in layers 2 and 3.

It should also be noted that the DSU 37 is not typically configured to detect all types of error conditions that may occur along the primary data path. For example, the DSU 37 is not normally configured to detect layer 3 error conditions, which usually occur within the primary network 22. FIG. 3 depicts an embodiment of the router 17 and DSU 37 that are collectively capable of detecting layer 3 error conditions and of backing up the primary data path based on such detections. The type of backup performed by the embodiment depicted by FIG. 3 will be referred to herein as “layer 3 backup.”

The components of FIG. 3 essentially perform the same functionality as the components of corresponding reference numbers of FIG. 2. In particular, when the router 17 receives a data packet to be routed to router 19, the IP stack 52, based on the routing table 59, transmits the data packet to one of a plurality of network interfaces 56 a-56 c based on information in the routing table 59. More specifically, prior to the detection of an error condition, the IP stack 52 transmits the data packet to either network interface 56 a or 56 b. The network interface 56 a or 56 b that receives the data packet then provides the data packet to frame relay protocol stack (FRPS) 89, which comprises virtual circuits 63 a and 63 b, as well as frame relay protocol port 66 a.

Each of the network interfaces 56 a-56 c corresponds to a different virtual circuit 63 a-63 c. In particular, network interfaces 56 a and 56 b respectively correspond to virtual circuits 63 a and 63 b of the frame relay protocol stack 89, and the network interface 56 c corresponds to virtual circuit 63 c of frame relay protocol stack 90. The virtual circuit 63 a or 63 b corresponding to the network interface 56 a or 56 b that processes the aforementioned data packet receives the data packet and, after processing the data packet, provides the data packet to the frame relay protocol port 66 a. The frame relay protocol port 66 a interfaces the data packet with the T1 interface 74, and the T₁ interface 74 then transmits the data packet across connection 31 such that the data packet is communicated via the primary data path to the router 19 (FIG. 1).

In the embodiment depicted by FIG. 3, router control logic 95 is configured to detect a layer 3 error condition. Such a detection may occur in a variety of ways. For example, in normal operation, the IP stack 52 and primary network 22 typically exchange messages according to the protocol employed by the primary network 22. Thus, the network 22 may simply inform the IP stack 52 of a layer 3 error condition detected by the network 22. In another example, the IP stack 52 may be configured to detect a layer 3 error condition if a specified amount of time lapses without receiving a message from the network 22. Note that a layer 2 problem or failure may result in the IP stack 52 not receiving messages from the network 22. In such an example, the layer 2 problem or failure may prevent proper layer 3 operation thereby causing the IP stack 52 to detect an error condition.

When the IP stack 52 detects an error condition, the router control logic 95 adjusts the routing table 59 such that data packets destined for the router 19 (FIG. 1) are no longer transmitted to one of the network interfaces 56 a or 55 b but are instead transmitted to the network interface 56 c. Note that the routing table of the router 19 should be similarly adjusted to reflect the foregoing changes.

As a result of updating the routing table 59, as described above, each data packet destined for the router 19 is processed by the frame relay protocol stack 90 instead of the frame protocol relay stack 89. In particular, each such data packet is processed by the virtual circuit 63 c and provided to the modem 88 via the frame relay protocol port 66 b. The modem 88 then communicates the data packet to the router 19 via the secondary data path. Thus, by appropriately controlling the routing table 59, as described above, it is possible to use the secondary data path to backup the primary data path. Unfortunately, the detection of error conditions by the IP stack 52 and subsequent updating of the routing table 59 to effectuate the layer 3 backup, as described above, can take a relatively long time thereby increasing the amount of data that may be lost due to an occurrence of a layer 2 or 3 error condition.

FIG. 4 depicts a communication network 100 in accordance with an exemplary embodiment of the present invention. Although other protocols may be employed, the network 100 is preferably configured to communicate via internet protocol (IP). For simplicity, the network 100 is shown in FIG. 4 as having two routers 110 and 120 capable of communicating to one another via a primary network 22 and/or a secondary network 25. However, it should be noted that the network 110 may employ other routers (not shown) in which each router is capable of communicating via an arrangement similar to the one depicted by FIG. 4.

In a preferred embodiment, the primary network 22 is a frame relay network that is respectively coupled to routers 110 and 120 via connections 31 and 33, and the connections 31 and 33 are TI connections or some other high speed connections. However, in other embodiments, the primary network 22 may be another type of network without departing from the principles of the present invention.

The secondary network 25 may be any type of known or future-developed network. For illustrative purposes, it will be assumed hereafter that network 25 is capable of communicating data between connections 41 and 43 via point-to-point protocol (PPP). As will be described in more detail hereafter, the primary network 22 and connections 31 and 33 preferably form a primary data path between routers 110 and 120. Further, the secondary network 25 and the connections 41 and 43 preferably form a backup data path between routers 110 and 120.

FIG. 5 depicts a more detailed view of an exemplary embodiment of the router 110. Note that the router 120 may be similarly configured. As shown by FIG. 5, components for implementing layers 1-3 are integrated into the router 110. In particular, layer 3 comprises, similar to the layer 3 of the router 17 depicted by FIG. 3, an IP stack 52, router control logic 95, and network interfaces 56 a and 56 b. In addition, layer 2 of the router 110 comprises, similar to the layer 2 of the router 17 depicted by FIG. 3, virtual circuits 63 a-63 c and frame relay protocol stacks 66 a and 66 b. Layer 2 also comprises a switch 140, which will be described in more detail hereafter.

Unlike the layer 1 components depicted by FIG. 3, the layer 1 components of FIG. 5 are integrated into the router 110 rather than residing external to the router 110, although it is possible for the layer 1 components to be external to the housing that houses components of layers 2 and/or 3. In particular, layer 1 of the router 110 preferably comprises two communication interfaces (e.g., T1 interface 74 and modem 88), although other numbers and types of communication interfaces may be employed in other embodiments, if desired.

Similar to the router 17 of FIG. 3, the router 110 of FIG. 5 is initially configured to communicate data packets destined for router 120 via a primary data path. In this regard, prior to a detection of an error condition, the IP stack 52 interfaces a data packet destined for the router 120 with one of the network interfaces 56 a or 56 b, depending on the data stored in the routing table 59. The foregoing network interface 56 a or 56 b then provides the data packet to its corresponding virtual circuit 63 a or 63 b within the frame relay protocol stack 89. The corresponding virtual circuit 63 a or 63 b that receives the data packet processes the data packet, as described above, and then provides the data packet to frame relay protocol port 66 a. The frame relay protocol port 66 a then provides the data packet to the TI interface 74, when interfaces the data packet with the primary network 22 via connection 31. The network 22 then communicates the data packet to the connection 33, which provides the data packet to the router 120. Note that data may be transmitted from the router 120 to the IP stack 52 of the router 110 in the opposite direction via the same data path.

As shown by FIG. 5, the router 110 preferably comprises monitoring logic 150 that is configured to detect layer 1, layer 2, and layer 3 error conditions. In response to a detection of a layer 1, 2, or 3 error condition, the monitoring logic 150 may switch out least one of the virtual circuits 63 a or 63 b in favor of a backup virtual circuit 63 c for communicating data packets over the secondary data path. In this regard, the monitoring logic 150 preferably communicates with the T1 interface 74, the frame relay protocol stack 89 of the primary data path, and the router control logic 95. The T1 interface 74 may be configured to detect a layer 1 error condition, and the IP stack 52 may be configured to detect a layer 3 error condition. Furthermore, the frame relay protocol stack 89 may be configured to detect a layer 2 error condition. When any such error condition is detected, the detecting component 74, 95, or 89 informs the monitoring logic 150 of the detected error condition. In response, the monitoring logic 150 controls the state of the switch 140 in order to switch communication from the primary data path to the backup data path.

As an example, assume that an error condition is detected, in block 181 of FIG. 6, that prevents data communicated by the virtual circuit 63 b from reaching its destination (e.g., router 120). In such an example, the monitoring logic 150, in response to the detected error condition, changes the state of the switch 140 such that data packets from the network interface 56 b are provided to virtual circuit 63 c instead of virtual circuit 63 b, as shown by block 183. The virtual circuit 63 c then properly processes the data packet for transmission over the secondary data path. Note that, in a preferred embodiment, data packets communicated over the secondary data path are communicated via PPP, although other types of protocols may be employed in other embodiments. After processing the aforementioned data packet, the frame relay protocol stack 90 provides the data packet to the modem 88, which communicates the data packet across the secondary network 25 and the connections 41 and 43 to the router 120.

After switching the communication of data packets to the backup data path, as described above, the monitoring logic 150 preferably continues to communicate with the T1 interface 74, the frame relay protocol stack 130 a, and/or the router control logic 95 to determine when the previously detected error condition is resolved. For example, if the aforedescribed error condition is detected because the frame relay protocol stack 89 stopped receiving messages from the primary network 22, then the monitoring logic 150 may determine that the previously detected error condition is resolved when the frame relay protocol stack 89 begins to receive messages from the network 22. In other examples, other techniques for determining that a previously detected error condition has been resolved may be employed.

When the monitoring logic 150 determines that the previously detected error condition has been resolved, the monitoring logic 150 preferably switches, to the primary data path, the communication occurring across the secondary data path, as shown by blocks 185 and 187 of FIG. 6. In this regard, the monitoring logic 150 adjusts the state of the switch 140 such that data packets from network interface 56 b are provided to the virtual circuit 63 b instead of the virtual circuit 63 c. Thus, such data packets are processed by the virtual circuit 63 b and are transmitted over the primary data path via the T1 interface 74.

Note that the switching from the primary data path to the secondary data path and vice versa is preferably transparent to layer 3 and, in particular, the IP stack 52. In this regard, once an error condition occurs, the IP stack 52 continues to process each data packet as if the data packet is to be communicated over the packet's primary data path. However, the monitoring logic 150, upon detecting the error condition, causes the data packets from the network interface 56 b to be communicated over the secondary data path rather than the primary data path. It is not necessary for the IP stack 52 to be aware of the data path switch, and it is not necessary for the routing table 59 to be updated to effectuate such a data path switch. Thus, the router 110 is able to complete a data path switch after the occurrence of a layer 2 or 3 error condition much quicker than the router 17 depicted by FIG. 3.

It should be noted that the communication occurring across other virtual circuits (e.g., virtual circuit 63 a) in the frame relay protocol stack 89 may be similarly backed up via an additional frame relay protocol stack (not shown) similar to frame relay protocol stack 90. In such a case, an additional switch (not shown), similar to switch 140, may be used to divert, in response to a detected error condition, data packets from the network interface 56 a to the virtual circuit (not shown) of the additional frame relay protocol stack. When the detected error condition is resolved, the additional switch may then be used to divert data packets from the network interface 56 a back to the virtual circuit 63 a of the frame relay protocol stack 89.

Furthermore, it should also be noted that the protocol stacks 89 and 90 are preferably compatible with the primary network 22. Thus, if a different type of primary network 22 is employed, then protocol stacks compatible with this other type of primary network 22 are preferably employed in lieu of the frame relay protocol stacks depicted in FIG. 5. In addition, the network interfaces 56 a and 56 b, unlike the protocol stacks 89 and 90, are preferably independent of the protocol employed by the primary and secondary networks 22 and 25.

It should be further noted that each of the components of layers 1-3 depicted in FIG. 5 may be implemented in hardware, software, or a combination thereof. However, according to ISO/OSI standards, layer 1 components are generally implemented in hardware, and layer 2 and 3 components are generally implemented in software. To be consistent with such standards, each of the components of layer 2 and 3 are preferably implemented in software as illustrated by way of example in FIG. 7.

In this regard, as shown by FIG. 7, the IP stack 52, router control logic 95, network interfaces 56 a and 56 b, switch 140, and frame relay protocol stacks 89 and 90 are implemented in software and stored within memory 152. The monitoring logic 150, which is outside the ISO/OSI layers, may be implemented in hardware, software, or a combination thereof. In FIG. 7, the monitoring logic 150 is illustratively shown as being implemented in software and stored within the memory 152.

Note that the components of the router 110, when implemented in software, can be stored and transported on any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch and execute instructions. In the context of this document, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport a program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable-medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. Note that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.

The exemplary embodiment of the router 110 depicted by FIG. 7 comprises at least one conventional processing element 155, such as a digital signal processor (DSP) or a central processing unit (CPU), that communicates to and drives the other elements within the router 110 via a local interface 158, which can include at least one bus. Each of the components of the router 110 is preferably housed within a single housing unit 163, although such a feature is not necessary for implementing the present invention.

It should be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims. 

1. A network router, comprising: a layer 1 portion having a first communication interface and a second communication interface, said first communication interface configured to communicate with a first network over a first data path and said second communication interface configured to communicate with a second network over a second data path; a layer 3 portion having a routing table, said layer 3 portion configured to provide a plurality of data packets destined for a particular destination; a layer 2 portion configured to interface at least one of said data packets with said first communication interface; and switching logic configured to automatically initiate a layer 2 switch such that said layer 2 portion begins to interface said data packets with said second communication interface in lieu of said first communication interface, wherein said layer 2 switch is transparent to said layer 3 portion.
 2. The router of claim 1, where said switching logic is configured to automatically initiate said layer 2 switch in response to a detection of an error condition associated with said first data path, and wherein said switching logic is further configured to automatically initiate another layer 2 switch, in response to a detection that said error condition is resolved, such said layer 2 portion begins to interface said data packets with said first communication interface in lieu of said second communication interface.
 3. The router of claim 1, wherein said second communication interface is configured to communicate using point-to-point protocol (PPP).
 4. The router of claim 1, wherein said first data path comprises a T1 link.
 5. The router of claim 4, wherein said second communication interface comprises a modem.
 6. A network router, comprising: a first protocol stack configured to provide a plurality of data packets to be transmitted by said router to a particular destination; a second protocol stack; a third protocol stack; a plurality of network interfaces configured to receive data packets from said first protocol stack, wherein said first protocol stack is configured to provide each of said plurality of data packets to one of said network interfaces; and switching logic configured to receive each of said plurality of data packets from said one network interface, said switching logic configured to provide at least one of said plurality of data packets to said second protocol stack and to provide, in response to a detection of an error condition, at least one other of said plurality of said data packets to said third protocol stack.
 7. The system of claim 6, further comprising: a first communication interface configured to transmit, over a first data path to said particular destination, each of said plurality of data packets provided to said second protocol stack; and a second communication interface configured to transmit, over a second data path to said particular destination, each of said plurality of data packets provided to said third protocol stack.
 8. The system of claim 7, wherein said protocol stacks, said network interfaces, said switching logic, and said communication interfaces are each integrated within a housing unit.
 9. The router of claim 6, wherein said first protocol stack is within a layer 3 portion of said router, and wherein said second and third protocol stacks are both within a layer 2 portion of said router.
 10. The router of claim 6, wherein said switching logic is configured to provide at least one of said plurality of data packets to said second protocol stack in response to a determination that said error condition has been resolved.
 11. A method for use in a network router, comprising the steps of: providing, from a layer 3 portion of said network router, data packets destined for a particular destination; interfacing a first plurality of said data packets with a first communication interface of a layer 1 portion of said network router; communicating said first plurality of data packets from said first communication interface over a primary data path; detecting an error condition associated with said primary data path; automatically performing a layer 2 switch in response to said error condition; interfacing, in response to said layer 2 switch, a second plurality of said data packets with a second communication interface of said layer 1 portion; and communicating said second plurality of data packets from said second communication interface over a backup data path, wherein said layer 2 switch is transparent to said layer 3 portion.
 12. The method of claim 11, further comprising the steps of: automatically initiating a second layer 2 switch in response to a detection that said error condition has been resolved; interfacing, in response to said second layer 2 switch, a third plurality of said data packets with said first communication interface; and communicating said third plurality of data packets from said first communication interface over said primary data path.
 13. The method of claim 11, wherein said communicating said second plurality of data packets is performed using point-to-point protocol (PPP).
 14. The method of claim 11, wherein said second communication interface comprises a modem.
 15. The method of claim 14, wherein said primary data path comprises a TI link.
 16. A method for use in a network router, comprising the steps of: using a layer 3 protocol stack within said network router to provide a plurality of data packets destined for a particular destination; transmitting said data packets from a first layer 1 communication interface over a primary data path and from a second layer 1 communication interface over a backup data path; transmitting each of said data packets to one of a plurality of layer 3 network interfaces within said network router; detecting an error condition associated with said primary data path; transmitting said data packets from said one layer 3 network interface to a plurality of layer 2 protocol stacks within said network router; and controlling which of said layer 2 protocol stacks receives each of said data packets based on said detecting step, wherein each of said data packets received by a first one of said layer 2 protocol stacks is transmitted over said primary data path and each of said data packets received by a second one of said layer 2 protocol stacks is transmitted over said backup data path. 